1. Field of the Invention
This invention pertains in general to the field of hip bone fixation and hip bone replacement devices and in particular to the field of combination apparatus for replacing the femoral head, reattaching a femoral head, and for fixing and compressing intra-trochanteric and sub-trochanteric fractures of the hip bone.
2. Description of the Prior Art
In the prior art, a device known as a compression hip screw, such as that described in my U.S. Pat. No. 4,657,001, issued Apr. 14, 1987, entitled Antirotational Hip Screw, is typically used for operative reduction and internal fixation of a femoral head or neck fracture of the hip bone. In general, these devices comprise a compression plate with a barrel attached thereto and extending therefrom at an angle of approximately 135.degree., and a lag screw. The compression plate typically attaches to the outside surface of the femur at the upper end thereof by ordinary screws. The barrel portion within which fits the lag screw, extends through a hole in the neck of the femur and into the head thereof. The lag screw compresses the fracture between the neck and the head, thereby allowing the same to permanently re-attach itself. The barrel attachment to the compression plate must offset the moment load applied to the femur as a result of force downward on the femoral head, and, therefore, is the one "weak link" of these prior art devices. The use of these prior art devices has been successful and substantially trouble-free. Patients having this type of apparatus used to join a broken head from the neck of a femur have been known to be as physically active after the operation as before the operation.
In the prior art, the device most commonly used to replace a femoral head which has become non-functional, comprises an implantable prothesis which includes a one-piece replacement head and femoral neck attached to a relatively large stem, the latter of which fits within a large hole prepared axially in the femoral bone through the upper end thereof. In the early prior art, the stems were cemented within the femoral cavity by the use of a plastic cement. Typically, the cement deteriorates with age, and due to the constant cyclic loading applied to the stem of the prosthesis by the action of simple walking, causes the cement to fracture and break loose from the femoral cavity, thereby requiring another operation to re-fix the prosthesis. Due to the soft nature of the femur and the generally advanced age of the patients needing this type of implant, it is sometimes difficult if not impossible to adequately re-fix the stem of the femoral process within the femoral cavity. When this condition occurs, the patient is often times restricted to the use of wheelchair.
Due to the many problems associated with cementing a femoral hip prothesis within the femur, a cementless type of implant has recently emerged and has been quickly accepted by the orthopedic community as the replacement for the cemented type of hip prothesis. The cementless type of hip prosthesis includes a porous surface over the length of the stem such that natural occurring bone growth after surgery grows into the porous surface of the stem, thereby firmly fixing, at least in theory, the femoral stem within the femoral cavity. The use of this cementless type of device requires that the patient be relatively immobile for a number of weeks following the surgery in order to allow the bone growth to occur and thereafter restrict his physical activities until a firm bond is created. These periods of time may involve a full twelve months.
The cementless type of femoral hip prosthesis is now in wide spread use today. One problem associated with this cementless type of hip prosthesis is the relatively long recovery period of time mentioned above. Another problem is the need for bone growth to occur to firmly fix the implanted prosthesis. Sometimes, the patient's physical activities, however restricted, still prevent firm bonding of the prosthesis to the femur. Another problem is that it is very difficult to remove a firmly bonded prosthesis should a failure of the prosthesis occur after surgery. The removal problem, although very significant, has assumed secondary status because of the relatively good adhesion provided by the bone growing into the porous surface of the stem portion. Notwithstanding the advantages of the cementless type of hip prosthesis as compared to the cemented type of hip prosthesis, there are occasions, all to frequently, where the implant of the hip prothesis fails requiring another operation to attempt to fix the same.
In either of the two types of hip prosthesis of the prior art, that is the cemented type and the non-cemented type, the problem still exists where the stem does not adhere to the femoral cavity causing loosening of the prosthesis and subsequent failure of the bone joint. In these instances, it often very difficult to re-insert another femoral hip prosthesis and have the same subsequently firmly affix itself within the femoral cavity.
Accordingly, there still exists a definite need for a total hip arthroplastic prosthesis which does not deteriorate with use and require subsequent replacement.
A primary objective of the present invention is to provide a total hip prosthesis wherein the femoral head of a femur is replaced and which replacement does not become loose during use.
Another object of the present invention is to provide a total hip prosthesis which, if necessary, may be easily removed a number of years following the initial surgery.
Another object of the present invention is to provide a total hip prosthesis which allows a patient to be substantially completely mobile after the operation.
Another object of the present invention is to provide a total hip prosthesis which can also be used to compress and fix fractures of the upper portion of a femur such as a neck break, an intratrochanteric break, and subtrochanteric fractures.
Another object of the present invention is to provide compression hip screw apparatus and total hip replacement apparatus having significantly improved strength characteristics to reduce the moment loads imposed by the offset load applied to the head of the femur which must translate along the neck of the femur and be reacted by the body proper of the femur.
The above-stated objects as well as others objects which although not specifically stated, but are intended to be included within the scope of the present invention, are accomplished by the present invention and will become apparent from the hereinafter set forth Detailed Description of the Invention, Drawings, and the claims appended herewith.